There have been concerns over carbon-induced climate change and the increasing demand for electrical energy. The increase in demand for electrical energy can be attributed to each person using more electrical appliances and more transport and heating being powered by electricity.
In recent times there has been a trend to increase the capacity of cleaner electricity generation and to persuade consumers to modify their electricity usage. One way consumers can modify their electricity usage is to reduce their overall electricity consumption. However other benefits can be derived from consumers modifying how they consume electricity.
For example, consumers' electricity usage can be modified using a known set of techniques called Demand-Side Management (DSM) which comprises measures such as improving building insulation and building automation.
Demand Response (DR) is another known technique for modifying consumer's electricity usage. DR comprises reducing or time shifting electrical loads carried out either manually by a user or automatically.
Time shifting electrical loads can be useful for modifying the time of day when a consumer places a load on the electrical transmission and distribution network and in turn the electrical generation connected thereto. In particular, the overall electricity demand on a transmission and distribution network varies over the course of a day. For example, in certain countries peaks in electricity demand often occur in the evening and early in the morning when people are using electrical appliances at home. Supplying this varying load can be challenging for the electricity transmission and distribution network operators and electricity generators. The electricity transmission and distribution networks have to be scaled for the peak demand and generators would prefer to supply a constant base load without substantial variations.
Previously some financial incentives have been used to implement DR. Some electricity suppliers have provided a lower cost night-time electricity tariff for domestic consumers. Some industrial electricity consumers have agreements with the electricity supplier or network operator to reduce loads at peak times.
Once recent concept is a demand response aggregator which recruits electricity consumers who are willing to reduce or to time shift their electricity consumption. In this way the DR aggregator can offer the system supply operator the option of time shifting or reducing a larger aggregated load from the networks. This concept is also known as “negawatt” generation. In this way a DR aggregator can offer the system operator the option of negative electricity generation during times of peak load in the same way an electricity generator can offer conventional electricity generation.
In some countries, such as the UK, the system operator can pay for balancing services to help match supply and demand, particularly at peak times. Balancing services can vary by one or more factors and depending on the type of the balancing service, the amount paid by the system operator can vary. The factors affecting balancing services comprises one or more of the following: response time from a request to curtail a load or time shift a load; availability of curtailment capacity or load time shift capacity; time availability of the curtailment capacity or load time shift capacity; time period for which the load can be curtailed or time shifted; and the number of times per year the load can be curtailed and/or time shifted. This means a DR aggregator can be paid for balancing services and share these earnings with its recruited consumers. In particular the most valuable balancing service is a fast response load adjustment for electrical system frequency control, as the mains system frequency deviates from the ideal when there is an imbalance of supply and demand on the system.
Known solutions for implementing DR comprise manually or automatically switching off a load at the request of the system operator, via a supplier or aggregator. In the industrial and commercial sectors loads can be switched off automatically based on information relating to the electricity transmission network or perhaps manually based on information received over the telephone.
Domestic applications of DR are not yet widespread, partly because there is a need for a behaviour change by the consumers. For example, consumers in the residential sector are required to turn off e.g. air conditioning units or swimming pool pumps during peak times. However depending on the type of appliance the consumer is using, the consumer may not be willing to turn off their appliance or postpone using their appliance, for example a heater or a cooker, during peak periods. Furthermore, in some countries like the UK, there are a limited number of appliances which a consumer may be willing or able to turn off during a peak period. Moreover the cost of DR automation equipment can be substantial.
Another known way to implement DR in the domestic environment is to use smart plugs which comprise a processor which determines when to turn off an appliance based on various information. However, some appliances are not suitable for use with a smart plug which interrupts the electricity supply and the appliance, for example a washing machine, may not return to the same state after an interrupted electricity supply resumes.
An uninterruptible power supply (UPS) is a known way to supply electricity to a load, for example servers and the like. A UPS receives electricity from a mains electricity supply and in turn supplies mains energy to devices plugged into it whilst charging an internal battery at the same time. The UPS keeps the battery charged so that if the input supply is lost, the battery can be used to generate an equivalent mains output to the load for a limited time period. This means the load does not experience an interruption in its electricity supply. However, the current UPS systems are expensive and require that the UPS is rated higher than the load attached.